This invention relates generally to crop feed handling apparatus and more particularly to a machine for grinding and mixing crop feed utilizing a speed responsive, positively engaging overload protective device mounted to the drive means to protect and prevent damage from occurring to the material infeed means by preventing plugging or jamming in the hammermill. Crop feed grinding and mixing machines, commonly called grinder-mixers, are normally provided with a mobile frame and a generally vertical extending mixing tank mounted on the frame. A hammermill is carried on the frame and provided with a hopper to receive feed material. The hammermill is used to grind desired types of crop feed materials before these materials are conveyed to the mixing tank as an additive to the feed mixture. The hammermill, of necessity, must be able to handle many different types of crop feed materials.
The hammermill is driven through a series of shafts and belted sheaves or sprockets from the power take-off of a tractor. Any feed material, when deposited in sufficient quantities into the hammermill, under varying moisture content conditions can create an excessive load that will cause the hammermill to jam or, at least, slug and decrease in speed. Certain crops, such as hay, naturally will cause a greater load strain on the hammermill as crop accumulation occurs. Crops with high moisture content will have a similar effect. Under such conditions if the infeed mechanism, normally in the form of an infeed auger, does not decrease or stop entirely the flow of crop feed material to the hammermill, the hammermill will jam and potentially cause serious damage to the grinder-mixer and the tractor.
Recently grinder-mixers of the type shown in U.S. Pat. No. 4,026,528, issued May 31, 1977 to Kline et al have enjoyed increasing popularity in the agricultural industry. This increased popularity has resulted in increasing numbers of grinder-mixers being used and, coupled with the now universally accepted fact that higher nutrient feeds produce more profitable and marketably attractive livestock, has caused attention to be focused on improved ways to prevent damage to the grinder-mixer drive means in the event of jamming of the hammermill, to avoid such costly jamming and to provide an overload protective device whose operating efficiency is not susceptible to operating or weather conditions.
Prior grinder-mixers utilized a friction clutch type of overload protective device in a hammermill of the type generally illustrated by U.S. Pat. No. 3,510,075, issued May 5, 1970 to Mann et al and assigned to the assignee of the present invention. Such overload protective devices were particularly susceptible to the weather conditions and the conditions under which the grinder-mixers routinely were operated. Since the overload protective devices were friction type clutches, dust and dirt would accummulate on the clamping device, usually in the form of a clamping screw, and would resist its clamping and unclamping movement. This would require the shaft-mounted clutch to achieve greater rotational speed to cause the pivotable friction arm to pivot radially outwardly and in turn cause the self-clamping frictional surfaces to effectively engage. The friction clutch would engage the infeed mechanism to transfer crop feed material to the hammermill. More significantly, these friction type clutches would slip when operated in their normal working environments in wet, muddy, icy or the generally sloppy conditions frequently found on farms or feedlots. These factors, plus the inherent disadvantages of a friction clutch system, such as wear and sensitivity, required that frequent readjustments be made to the friction clutches. Additionally, the hypersensitivity of these types of clutches all too frequently resulted in the clutch being either adjusted too tightly so that it would not disengage upon jamming or overloading or not being adjusted tightly enough so that the drive means slipped and crop feed material was transported to the hammermill at less than the optimum rate. The friction contact surfaces also required periodic and costly replacement during normal operating conditions. Lastly, these types of overload protective clutches were extremely costly to manufacture because of the high cost friction design material required.
The foregoing problems are solved in the design of the machine comprising the present invention by providing a positively engaging, functionally nonfriction dependent centrifugal clutch that automatically disengages the material infeed means from the drive means whenever excessive crop feed accumulation occurs in the grinding means and causes the drive means to be slowed in operation below a predetermined speed. The grinding means, in the form of a hammermill, continues to operate without any additional crop feed being delivered to it until the drive means returns to the predetermined speed, at which time the material infeed means is automatically reengaged by the positively engaging functionally nonfriction dependent centrifugal clutch to permit the flow of crop feed to recommence.